The purpose of such an intermediate storage device basically consists in the fact that product units arranged beside one another in a row are at all times made available without gaps to a continuously delivering conveyor arrangement—which for its part feeds, for example, a following processing or packaging unit with product units to be processed. In the case of excesses in the supply, the product units can be diverted temporarily into the intermediate storage arrangement and, in the case of gaps in the supply, product units can be removed from the intermediate storage arrangement.
Intermediate storage functions are of particular importance in production lines. It is also a matter of ensuring, for example, the removal of product units from the upstream production units when a stoppage occurs in a downstream processing or packaging unit, in order that production as a whole does not have to be stopped. Such downtimes occur not only in the event of mishandling operations or defects, but in some cases are also quite regular, e.g. when there is a change-over from one size or shape of product units or packaging units to another size or shape. This may require various further adaptations, such as for example carriers, grippers or spikes for engaging product units in various stations of a production line. If, on the other hand, a station upstream in the production line is stopped, the downstream stations can be temporarily fed from the intermediate storage arrangement. It is also often the case that the individual stations may be operated in a controlled manner at different speeds in order to fill or empty the existing intermediate storage arrangement.
EP-1 114 784 shows a device for taking over elongated, at least approximately cylindrical product units, in particular tubes, sleeves or cans, which are coming continuously from a production line. The device is used to form product groups with a preselectable number of units. It comprises a continuously supplying conveyor unit and a conveyor belt with product receptacles which takes up the product groups and conveys them into a diverting position. The conveyor unit and the conveyor belt also comprise a common transfer section in which they run spaced apart parallel to one another. In the region of the transfer section, a size-variable depositing area is disposed between the conveyor unit and the conveyor belt, said depositing area being able to be moved depending on the product groups to be formed. The size-variable depositing area is designed as a flexible belt section, which in a restricted sense can be regarded as an intermediate storage function. An essential drawback with this device, however, is that the available intermediate storage capacity is very small, because the main purpose of this device lies not in the intermediate storage, but in the formation of product groups.
Intermediate storage devices or compensators with a larger accommodation capacity are also known. They are usually devices with meandering chains, to which gondola-like shells are attached which can accommodate the product units. An example of such a compensator is described in EP-0 438 974.